LU-6142 all: use list_first_entry() where appropriate.

LU-6142 all: use list_first_entry() where appropriate.

Lustre already uses list_first_entry() in many places, but
it is not consistent.  Let's make it consistent.
The patch was generated with

 sed -i 's/list_entry(([^,]*)->next,/list_first_entry(1,/'
     `git grep -l 'list_entry(.*->next' lustre/ lnet/ libcfs/ `

followed by some manual cleanup of indents, and adding
list_first_entry() to libcfs/include/libcfs/util/list.h

Test-Parameters: trivial
Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: Id646fba1faf40282e66ede07c88c8db5ffadc211
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/50826
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>